This invention relates generally to the art of cutting, brazing, and gouging of metals, alloys and like materials, and specifically to a method of rapid cutting of metals.
In a typical metal cutting operation, a cutting torch is connected to a source of fuel gas and to a source of oxygen. The oxygen and fuel gas mixture is combusted while so juxtaposed with respect to a work piece, such as a metal plate or the like, that the work piece is first preheated, and then cut. After the metal which is to be treated has risen to a predetermined temperature, i.e. after the preheating stage is over, the percentage of oxygen in the oxygen fuel gas mixture is increased in order to increase the temperature of the flame. The increased temperature of the flame then provides a suitable source of heat for cutting, brazing, gouging or any similar process, such as welding or flame hardening.
Typical fuel gases include natural gas, propane, acetylene, and mixtures thereof. These gases, when combusted with oxygen, can provide very hot flames in the general range of from 4,500.degree.F. up to and perhaps slightly above 5,500.degree.F.
The cost of natural gas, propane, butane, and acetylene is not inconsequential. Therefore, it is desirable to have the greatest efficiency of treatment per quantity of industrial fuel gas employed. This is especially true when the supply of natural gas, propane, butane and acetylene is somewhat limited.
One measure of the efficiency of an industrial fuel gas is the quantity of gas needed to perform a given job. With respect to fuel gases utilized for metal working, such as metal cutting, another measure of efficiency is the cutting speed. A decrease in the quantity of fuel gas needed to perform a given cutting operation, coupled with an increase in cutting speed or capacity, will result in increased cost savings per foot of cut or like treatments. Thus, an ideal fuel gas would be one which would provide rapid treatment with a minimum quantity of fuel and oxygen employed.
In addition to the considerations mentioned above, the acceptability of a fuel gas is also determined by an examination of the quality of cuts, obtained when utilizing a certain fuel gas.
Yet another standard of measurement of the acceptability of a fuel gas is its affect upon the metal or alloy which is being treated. For example, subjecting high carbon containing steel alloys to high temperatures for extended periods of time is known to affect the crystal structure of the alloy itself. For example, the crystal lattice of the alloy may be changed from a body centered crystal structure to a face centered crystal structure, and as a result, the steel becomes harder and more brittle. The hardened steel in the absence of compensating heat treatment is, of course, much more difficult to machine. However, if a fuel gas could be developed which would satisfactorily complete a cut within a very short period of time, there may be insufficient time for the alloy to be deleteriously hardened.
Yet another important consideration in determining suitability of a given industrial fuel gas, and specifically those fuel gases utilized for cutting purposes, is the general appearance of the cut after it is made. A good cut is one which has a generally straight line appearance, little or no rollback, little or no evidence of burning of the metal, and little or no slag present along the line of the cut. Conversely, a bad cut is characterized by an irregular surface along the cut, a general appearance of dishing out along the cut, excessive slag along the line of the cut with the slag sticking to the cut and being very difficult to remove, and a general burned appearance over the line of the cut.
Yet another important attribute of a good quality fuel gas is that the gas must be completely combustible to carbon dioxide and water. Thus, gases which could potentially be useful industrial fuel gases but which will provide sulphur or nitrogen oxides as byproducts are unsuitable because of their undesirable pollution effects.
This invention relates to a method of flame cutting using a novel fuel gas composition, which makes possible the utilization of a minimum quantity of fuel gas to accomplish a given metal cutting task in a minimum of time, and provides a high quality cut, all without having a significant adverse effect upon the crystal structure characteristics of the metal being treated. In addition, the byproducts of the combustion of the industrial fuel gas compositions are nearly all carbon dioxide and water, indicating nearly complete combustion. Thus, there is no utilization of hazardous additives which will provide undesired polluting combustion byproducts such as sulphur dioxide and nitrogen oxides.
An application of the invention is illustrated more or less diagrammatically in the following drawing wherein: